Lecture 14 - Moulting animals Flashcards
Ecydsozoa
Moulting animals, descending from distant ancestors: Trilobite and Marella
Strengths and weaknesses of moulting
Allows damaged tissue and missing limbs to be regenerated or substantially reformed
The exoskeleton of arthropods cannot grow without moulting, leaving the animal vulnerable. An arthropod will moult several times during its life and is vulnerable for a period of time every time
Nematodes: what are they, what are their key features, how many species are there, and where can you find them?
Longitudinal organisms with collagen that absorbs oxygen. Lack of circular muscles causes whip-like movement
- Bilaterally symmetrical and triploblastic.
- Cylindrical in shape.
- Tissue-level organization.
- Cavity or Pseudocoelom.
- Alimentary canal is distinct
- Often parasitic
30,000 discovered but possibly more
Found everywhere: in/on organisms, water, water film, mud (one square meter is enough), soil (1 acre contains billions of nematodes), etc
Alimentary canal
The whole passage along which food passes through the body from mouth to anus during digestion.
Opisthosoma
The abdomen in spiders, contains the guts, heart, reproductive organs, and silk glands
Arthropods: what are they, what are their key features, how many species are there, and where can you find them?
Bilaterally symmetrical organisms with segments and jointed appendages usually with a chitin exoskeleton for protection and compound eyes
- Largest phyla
- Solid muscle anchor points
- Each segment has a pair of appendages
- Various forms of appendage (antennae, mouthparts, legs and more legs)
- Open circulatory system
- Have hemolymph instead of blood
- May have malpighian tubule
- May have mandibles (strong jaws)
Over one million discovered but up to ten million may exist
Everywhere.
Chelicerates: what are they, what are their key features, how many species are there, and where can you find them?
Two body segments: cephalothorax and abdomen without antennae but have six pairs of modified appendages
- Six appendages: four legs, chelicerae, pedipalps
- Chelicerae: modified appendages (pincers/fangs) * Pedipalps: small appendages leg/antennae-like that may be used for webs, feeding, sensing
- Absence of mandible and antenna
120,000 species: Pycnogonida (sea spiders), Merostomata (Xiphosurida (horseshoe crabs)), Arachnida (Araneae (spiders), Scorpiones (scorpions), Opiliones (harvestmen), Acari (ticks and mites)), etc
Largely terrestrial arthropods, living beneath stones and logs, in leaf mould, and in vegetation, but there are some aquatic mites that live in fresh water and in the sea.
Pycnogonida: what are they, what are their key features, how many species are there, and where can you find them?
“Sea spiders” that have an almost disappeared abdomen while the legs are long and clawed
- Larvae are not planktonic, so disperse slowly
- Carnivorous grazers – no digestive system
- Large surface area – absorb oxygen
- Males carry eggs and even larvae – close external fertilization
> 1,300 species
Found particularly in polar seas
Xiphosurida: what are they, what are their key features, how many species are there, and where can you find them?
An order of the Arthropoda phylum that, like chelicerates, has a body divided into two main subdivisions, the prosoma (head) and opisthosoma
- living fossils: existed nearly unchanged for at least 445 million years (before dinosaurs existed)
- Called horseshoe crab but closer to spider
- Long tail (telson) used to flip the organism
- Almost hunted to extinction until the hunting ban in 1970
Only 3 genera (4 species)
Found particularly in polar seas
Arachnids: what are they, what are their key features, how many species are there, and where can you find them?
A class of joint-legged invertebrates that contain six pairs of appendages: four pairs of legs, chelicerae, and pedipalps
- Cephalothorax (front) and abdomen (behind)
- Sexual dimorphism (female is larger)
- Zig-zag web structure (stabilimentum – unknown
function(s) - All spiders except one
species are carnivores
100,000 species
Spiders, scorpions, whip scorpions, mites,
Opiliones (harvestmen), Argiope spider (Spain)
Opiliones: what are they, what are their key features, how many species are there, and where can you find them?
The ‘weird’ spiders that do not produce silk, have a single body with an externally segmented abdomen
- Omnivores
- Penetrative sex
About 6500 species
Can be found in leaf litter, among foliage and in the grass in a wide variety of habitats.
Acari: what are they, what are their key features, how many species are there, and where can you find them?
Mites and ticks that have a single body part (the idiosoma) with four pairs of legs, chelicerae, and pedipalps
- Live in hair
- Absence of wings and antennae
- 0.1mm - 6mm size range
45,000+ species
Practically anywhere: hot springs, caves, harsh deserts, and tundras
Acari: what are they, what are their key features, and what animals?
Arthropods that have mandibles near their mouths
Include insects, crustaceans, and myriapods
Myriapods: what are they, what are their key features, how many species are there, and where can you find them?
Multilegged arthropods that have mandibles and respiratory exchange through a tracheal system
- Two body sections (head and trunk)
- One pair of antennae on the head
- Simple eyes
- Mandibles (lower jaw) and maxillae (upper jaw)
Nearly 13,000 species
Myriapods are most abundant and diverse in tropical and temperate forests
Diplopoda: what are they, what are their key features, how many species are there, and where can you find them?
Class of myriapod that contains two pairs of legs per segment (millipedes).
- Oldest known terrestrial animals
- Decomposers (especially deciduous forests)
- Monophyletic
- Trachaea and mandibles – like insects
- Thorax: four segments, each with 1 pair of legs, used in mating
- In some species, males brood eggs
Around 12,000 species
Mainly found in the soil, under rocks, or under the bark of trees
